<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<h1>Page2</h1>
		<script type="text/javascript">
			document.addEventListener('visibilitychange',e => {
				if(document.visibilityState === 'hidden') {
					document.title = 'page2隐藏中。。。';
				} else if(document.visibilityState==='visible'){
					document.title = 'page2又显示了';
				}
			})
		</script>
	</body>
</html>
